Manual pointing device for a computer system with inertial click-event detection and corresponding click-event detection method

ABSTRACT

A manual pointing device for a computer system, the device having at least one key that can be actuated manually by a user, and a click-event detection module coupled to the key for detecting actuation thereof. The click-event detection module is provided with an inertial sensor for detecting mechanical stresses generated by actuation of the key.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pointing device for a computer systemwith inertial click-event detection and to a corresponding click-eventdetection method.

2. Description of the Related Art

As is known, most computer systems and computer-controlled devices areprovided with pointing peripherals that enable commands to be impartedand a high number of operations to be executed in an extremely simpleand intuitive way. In particular, the mouse is now the most commoninterface between a user and a computer and is manually displaced on aplane or on a two-dimensional surface for controlling a cursor orpointing element displayed on a screen. For this purpose, the typicalmouse has a plurality of sensors that detect a movement in twodimensions of the mouse, a plurality of keys for entering commands, anda communication interface for communicating with the computer system.

In a conventional mouse, the keys actuate normally-openelectromechanical switches so as to modify the state of a recognitioncircuit, and are controlled directly by the user's fingers (usually, theindex finger and the middle finger). In use, the mouse is held by theuser in his hand, and the fingers rest on the keys, which are actuatedby exerting a slight pressure. To facilitate recognition of voluntaryacts by the user, the keys are triggered only if a sufficient force isapplied, higher than a pre-set threshold. Since triggering produces asound event, actuation of a key is typically defined as “click” or“click event”.

A drawback of traditional pointing devices is that the contacts of theswitches, with time, tend to oxidize, and hence electric-type detectionof the click events fails. Clearly, this problem renders unusabletraditional pointing devices and limits their average life.

BRIEF SUMMARY OF THE INVENTION

The disclosed embodiments of the present invention provide a pointingdevice that is an alternative to known devices that is free from thedrawbacks described above.

According to one embodiment of the invention, a manual pointing devicefor a computer system is provided that includes at least one first keymanually actuatable by a user, and a click-event detector coupled to thefirst key for detecting actuation of the first key, the click-eventdetector including an inertial sensor for detecting mechanical stressesgenerated by actuation of the first key.

In accordance with another aspect of the foregoing embodiment, theinertial sensor includes a first detection axis and a second detectionaxis, perpendicular to one another and parallel to a surface of slidingof the manual pointing device at least in one operative configuration,and a third detection axis perpendicular to the first and seconddetection axes; the inertial-sensor means supplying a first detectionsignal, a second detection signal, and a third detection signal inresponse to mechanical stresses acting along the first detection axis,the second detection axis, and the third detection axis, respectively.

In accordance with another aspect of the foregoing embodiment, thedevice includes a casing and the inertial-sensor is rigidly coupled tothe casing for detecting mechanical stresses generated by actuation ofthe first key and that propagate along the casing.

In accordance with another embodiment of the invention, a user inputdevice is provided that includes at least one element for generatingvibrations and a sensor configured to detect the vibrations. Ideally,the sensor is configured to detect vibrations along at least two axes ofdetection and preferably three axes of detection that are perpendicularto one another.

In accordance with another aspect of the foregoing embodiment, the atleast one element includes at least one manually actuated member that,ideally, is a depressible mechanical key mounted on a casing. Preferablythe sensor is configured to detect vibrations generated through thecasing by the at least one key.

In accordance with another aspect of the foregoing embodiment, a circuitis included in the user input device that is coupled to the sensor andconfigured to receive detection signals generated by the sensor and todetect displacement signals correlated to a respective key of the atleast one key. Preferably the circuit includes an interface forreceiving the displacement signals and providing the same to a computersystem.

In accordance with another embodiment of the invention, a user inputdevice for a computer system is provided that includes a movable casinghaving at least two manually disposable keys mounted thereon andtransmitting therethrough vibrations generated by the keys when the keysare manually depressed; a transducer mounted on the casing and adaptedto detect the vibrations and to generate a detection signal associatedwith vibrations generated from each key; and a circuit coupled to thetransducer and adapted to generate displacement signals responsive tothe respective detection signals.

In accordance with another aspect of the foregoing embodiment, thetransducer includes an accelerometer device having three axes ofdetection and supplying corresponding first, second, and third detectionsignals.

In accordance with another aspect of the foregoing embodiment, theaccelerometer device is mounted on a base that is mounted on the casingto rotate about the second detection axis.

In accordance with another aspect of the foregoing embodiment, thedevice includes a first mechanical-coupling element configured forexerting a pressure on the board asymmetrically with respect to thesecond detection axis when the first key is actuated so that the boardwill be inclined when rotated about the second detection axis, andwherein a second key of the at least two keys that can be actuatedmanually by a user, and in which the first and second keys are set inopposite positions with respect to the second detection axis, the secondkey having a second mechanical-coupling element configured for exertinga pressure on the board asymmetrically with respect to the second axiswhen the second key is actuated so that the board is inclined to rotateabout the second detection axis. The first and second keys and the firstand second mechanical-coupling elements are configured so that theinclination of the board produced by actuation of the first key isopposite to the inclination produced by actuation of the second key.

In accordance with another embodiment of the invention, a manual inputdevice is provided that includes a plurality of keys, each keyconfigured to generate a mechanical stress when manually actuated; atransducer device configured to detect mechanical stress generated fromactuation of each key and to generate a respective detection signal; anda circuit coupled to the transducer device to receive the detectionsignals and to generate in response thereto respective displacementsignals.

In accordance with another aspect of the foregoing embodiment, the keysare mounted to a casing, and the transducer is mounted on a board thatin turn is mounted to the casing to move about an axis of rotation whensubjected to mechanical stress from the keys, and the transducer ideallyincludes accelerometers to detect movement of the board about at leasttwo axes.

In accordance with a further aspect of the foregoing embodiment, thecircuit includes a detector that detects movement of the board andgenerates corresponding detection signals, and the circuit furtherincludes a processor that receives the detection signals and generatesdisplacement signals correlated to the actuated keys.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

For a better understanding of the invention, some embodiments thereofwill now be described, purely by way of non-limiting example and withreference to the attached plate of drawings, wherein:

FIG. 1 is a top plan view of a pointing device for a computer system,incorporating the present invention;

FIG. 2 is a lateral right-hand view of the device of FIG. 1, sectionedalong the plane of trace II-II of FIG. 1;

FIG. 3 is a top plan view of the device of FIG. 1, sectioned along theplane of trace III-III of FIG. 2;

FIGS. 4 and 5 are schematic views which illustrate the propagation ofmechanical stresses in the device of FIG. 1;

FIG. 6 is a simplified block diagram of the device of FIG. 1;

FIG. 7 is a more detailed block diagram of a part of the device of FIG.1;

FIG. 8 is a graph that represents quantities regarding the presentinvention;

FIG. 9 is a block diagram regarding a pointing device for a computersystem in accordance to a second embodiment of the present invention;

FIG. 10 is a top plan view of a pointing device for a computer systemaccording to a third embodiment of the present invention;

FIG. 11 is a lateral right-hand view of the device of FIG. 1, sectionedalong the plane of trace XI-XI of FIG. 12, of a pointing device for acomputer system according to a fourth embodiment of the presentinvention;

FIG. 12 is a front view of the device of FIG. 11, sectioned along theplane of trace XII-XII of FIG. 11;

FIGS. 13 and 14 are schematic front views transversely sectioned of thedevice of FIG. 11 in respective operative configurations; and

FIG. 15 is a block diagram corresponding to the device of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1-3, a manual pointing device for a computersystem, in this case a mouse 1, is illustrated in accordance with oneembodiment of the invention. The mouse 1 includes a casing 2 and a board3, on which are arranged a triaxial inertial sensor 4 and amicrocontroller 5.

The casing 2 is made of a substantially rigid polymeric material,suitable for favoring propagation of mechanical vibrations, and has alongitudinal plane PL of symmetry. A first key (left key) 7 and a secondkey (right key) 8 are arranged on the casing 2 and may be actuated by auser by exerting a slight pressure. The left key 7 and the right key 8are arranged on opposite sides and preferably in symmetrical positionswith respect to the longitudinal plane PL. Furthermore, the keys 7, 8are provided with a clicking mechanism (known and not shown) and henceexert a small impulse of force on the casing 2 when they are pressedwith a force sufficient or when they are released (click event).

The board 3 is rigidly connected to the casing 2, in such a way that,when the casing 2 receives an impulse of force, for example followingupon a click event, the vibrations thus generated will be transmitted tothe inertial sensor 4 through the board 3.

The inertial sensor 4 is mechanically coupled to the casing 2 throughthe board 3, for detecting movements of the mouse 1 and impulses offorce applied to the casing 2, according to three distinct mutuallyperpendicular detection axes. Preferably, the inertial sensor 4comprises a biaxial accelerometer and a uniaxial accelerometer, both ofwhich are made with the MEMS (micro-electromechanical system) technologyand are integrated in a same chip. For example, the biaxialaccelerometer is of the type described in the European patentapplication No. EP-A-1365211, whereas the uniaxial accelerometer is madeaccording to European patent application No. EP-A-1253399 filed on Apr.27, 2001 or to U.S. Pat. No. 5,955,668. In greater detail, a firstdetection axis X and a second detection axis Y are parallel to a planeof sliding PO of the mouse 1 (generally a horizontal plane, as in FIG.2), whereas a third detection axis Z, perpendicular to the first two, issubstantially vertical. Furthermore, the inertial sensor 4 is arrangedsuch that the second detection axis Y will lie in the longitudinal planePL of symmetry of the casing 2. Consequently, the left and right keys 7,8 are in opposite positions with respect to the second detection axis Y.The inertial sensor 4 generates a first analog acceleration signalS_(X), a second analog acceleration signal S_(Y) and a third analogacceleration signal S_(Z) correlated to the components of theaccelerations acting on the casing 2 according to the first detectionaxis X, the second detection axis Y, and the third detection axis Z,respectively (see also FIG. 6).

In practice, when one of the keys 7, 8 is pressed or released, thecorresponding click event generates a small force impulse whichpropagates to the inertial sensor 4 through the casing 2 and the board3. The inertial sensor 4, which is a MEMS sensor and is hence extremelysensitive, is capable of detecting the vibrations produced by theimpulse of force. Click events caused by the left key 7 and by the rightkey 8, which are opposite with respect to the second detection axis Y,produce stresses of opposite signs along the first detection axis X. Asshown schematically in FIGS. 4 and 5, in fact, at the position of theinertial sensor 4 the vibrations caused by click events propagate in thesame direction along the second detection axis Y, but in oppositedirections with respect to the first detection axis X. Furthermore, aclick event can be distinguished from a displacement of the mouse 1 inits plane of sliding PO because also a significant component ofacceleration along the third detection axis Z is associated to the clickevent, which in the case of a planar displacement is substantiallyabsent.

The microcontroller 5 uses the first, second and third analogacceleration signals S_(X), S_(Y), S_(Z) to recognize click events, todiscriminate click events produced by the left key 7 and by the rightkey 8, and to determine the displacements of the mouse 1.

With reference to the block diagram of FIG. 6, the microcontroller 5comprises a reading unit 9, a processing unit 10, and an interface 11,for connection to a computer system 12. The reading unit 9 is connectedto the inertial sensor 4 for receiving the first, second and thirdanalog acceleration signals S_(X), S_(Y), S_(Z). Furthermore, thereading unit 9 supplies: the inertial sensor 4 with control signals VFBand clock signals VCK necessary for reading; and the processing unit 10with a first digital acceleration signal D_(X), a second digitalacceleration signal D_(Y) and a third digital acceleration signal D_(Z),obtained from the analog-to-digital conversion of the first, second andthird analog acceleration signals S_(X), S_(Y), S_(Z), respectively.

On the basis of said signals, the processing unit 10 determines a firstdisplacement signal P_(X) and a second displacement signal P_(Y), whichindicate the displacements of the mouse 1 with respect to the first andto the second detection axes X, Y, respectively, and a first statesignal LMB and a second state signal RMB, which switch in response toclick events and indicate the state (pressed/released) of the left key 7and of the right key 8, respectively.

The interface 11 is connected to the processing unit 10 for receivingthe displacement signals P_(X), P_(Y) and the state signals LMB, RMB andtransmitting them to the computer 12 in a pre-determined standardformat. The interface 11 is of any type suitable for supportingcommunication with the computer system 12, for example, of an RS-232 orof a USB serial type. Alternatively, it is possible to provide anoptical (IR) connection or else to use the bluetooth technology.

With reference to FIG. 7, the processing unit 10 comprises a firstprocessing line 13, a second processing line 14, and a third processingline 15. The first and second processing lines 13, 14 receive from thereading unit 9 the first and second digital acceleration signals D_(X),D_(Y) and generate the first displacement signal P_(X) and the seconddisplacement signal P_(Y), respectively, on the basis thereof.

The third processing line 15 comprises a recognition module 17, adiscrimination stage 18, and a first memory element 20 and a secondmemory element 21.

The recognition module 17 receives at input the third digitalacceleration signal D_(Z) from the reading unit 9 and supplies on itsoutput a recognition signal CKDET, which indicates a stress directedalong the third detection axis Z and has values correlated to theoccurrence of click events. In greater detail, the recognition signalCKDET has a (positive) enabling value, when the third digitalacceleration signal D_(Z) is higher than a pre-set threshold D_(ZT), anda disabling value (zero) otherwise (see also FIG. 8). The recognitionsignal CKDET, consequently, switches to the enabling value in responseto a stress along the third detection axis Z (click event) and ismaintained constant until the stress ceases (typically, the duration ofthe perturbations associated to click events is of approximately 200-240ms). Furthermore, the recognition signal CKDET preferably switches againto the disabling value when a pre-determined time interval T₀ haselapsed after the third digital acceleration signal D_(Z) has droppedbelow the threshold D_(ZT) (for example, after 10 ms).

The discrimination stage 18 includes a derivative module 23, amultiplier node 24 and a sign discriminator 25. The derivative module 23receives at input the first digital acceleration signal D_(X) from thereading unit 9 and calculates the time derivative D_(X)′ thereof. Themultiplier node 24 has a first input 24 a and a second input 24 bconnected to the outputs of the derivative module 23 and of therecognition module 17, respectively, and multiplies the value of thetime derivative D_(X)′ of the first digital acceleration signal D_(X)with the value of the recognition signal CKDET. On the output of themultiplier node 24 a product signal S_(PX) is consequently present,which is normally zero, namely, when the mouse 1 is inactive or isdisplaced without the keys 7, 8 being actuated, and is proportional tothe value of the time derivative D_(X)′ when the recognition signalCKDET is at the enabling value, i.e., when a click event occurs.

The sign discriminator 25 is connected to the output of the multipliernode 24 for receiving the product signal S_(PX) and has a first outputand a second output connected to the first memory element 20 and to thesecond memory element 21, respectively. In the embodiment describedherein, the sign discriminator 25 supplies first click impulses LCK onthe first output and second click impulses RCK on the second output. Thefirst and second click impulses LCK, RCK indicate click events caused bythe pressure or release of the left key 7 and of the right key 8,respectively. In practice, the sign discriminator 25 generates a firstclick impulse LCK when the product signal S_(PX) has a negative sign anda second click impulse RCK when the product signal S_(PX) has a positivesign; no impulses are generated if the product signal S_(PX) is zero.Since the left key 7 and the right key 8 are arranged in oppositepositions with respect to the second detection axis Y, the click eventscorresponding to the left key 7 and the click events corresponding tothe right key 8 produce stresses of opposite sign along the firstdetection axis X. In other words, the first digital acceleration signalinitially has a positive or negative peak, according to whether theclick event regards the left key 7 or to the right key 8. The sign ofthe peak is readily identifiable by considering the sign of the timederivative D_(X)′, and each click event can be selectively associated tothe left key 7 or else to the right key 8.

The first and second memory elements 20, 21 are, for example, “T” typeflip-flops and switch whenever they receive an impulse at input. Outputsof the first and second memory elements 20, 21 supply the first andsecond state signals LMB, RMB, respectively. Then, the first and secondmemory elements 20, 21 switch in response to click events produced bythe left key 7 and by the right key 8, respectively, and the values ofthe state signals LMB, RMB indicate the state (pressed/released) of theleft key 7 and of the right key 8, respectively.

Preferably, a reset module 23 is associated to the memory elements 20,21 and restores a configuration corresponding to the state of keyreleased when pre-determined conditions arise (for example, apre-determined time of a few seconds elapses without any click eventsoccurring).

In practice, the processing unit 10 recognizes that a click event hasoccurred using the third digital acceleration signal D_(Z), which iscorrelated to the vibrations imparted on the casing 2 of the mouse 1 ina direction perpendicular to the plane of sliding PO of the mouse 1itself. The stresses caused by the click events are discriminated fromthe accelerations due to the normal movement of the mouse 1 since aclick event also causes perturbations directed as the third detectionaxis Z. During displacement of the mouse 1, instead, the component ofacceleration along the third detection axis Z is substantially zero. Inother words, recognition of click events is selectively enabled by therecognition module 17 in the presence of a peak of the third digitalacceleration signal D_(Z) and disabled otherwise, on the basis of therecognition signal CKDET. The multiplier node 24 functions as enablingelement controlled by the recognition module 17. In addition, theprocessing unit 10 is able to associate a click event to the left key 7or to the right key 8 according to the sign of the time derivativeD_(X)′ of the first digital acceleration signal D_(X).

A different embodiment of the invention is illustrated in FIG. 9, inwhich parts that are the same as those already shown are designated bythe same reference numbers. In this case, the outputs of the recognitionmodule 17 and of the derivative block 23 are connected to a controlinput 30 a and to a first data input 30 b of a selector 30. A seconddata input 30 c of the selector 30 is, instead, connected to a referenceblock 31, which supplies constantly the value zero. The output 30 d ofthe selector 30 is connected to the sign discriminator 25. The selector30 is controlled in such a way that the output 30 d is connected to thefirst data input 30 b in the presence of the enabling value of therecognition signal CKDET, and to the second data input 30 c otherwise.In practice, then, the sign discriminator 25 receives the timederivative D_(X)′ of the first digital acceleration signal D_(X) inresponse to a click event, when the recognition signal CKDET has theenabling value, and the value zero otherwise.

In the embodiment of FIG. 10, a mouse 100 comprises a front key 107 anda rear key 108 arranged in respective opposite positions with respect tothe first detection axis X of a MEMS inertial sensor 105. Consequently,detection of the click events is based upon the second digitalacceleration signal D_(Y) and upon its time derivative D_(Y)′. Differentkey arrangements are in any case possible.

According to a further embodiment of the invention, shown in FIGS.11-15, a mouse 200 comprises a casing 202, provided with a left key 207and a right key 208, and a board 203, set on which are a triaxialinertial sensor 204 and a microcontroller 205. In particular, theinertial sensor 204 has a first detection axis X, a second detectionaxis Y, and a third detection axis Z, which are mutually perpendicular.The first and second detection axes X, Y are parallel to the plane ofthe board 203, whereas the third detection axis Z is perpendicularthereto. In addition, the second and third detection axes Y, Z togetheridentify a median longitudinal plane of the mouse 200. Furthermore, theleft key 207 and the right key 208 are arranged in opposite positionswith respect to the median longitudinal plane and to the seconddetection axis Y.

The board 203 is mechanically connected to the casing 202 so as to bemaintained substantially parallel to a plane of sliding PO of the mouse200 (normally horizontal) and so as to present, moreover, a margin ofmobility with respect to the casing 202 itself. In greater detail, fourguide screws or pins 206, provided with respective heads 206 a, areinserted with play in as many through holes 209 made on the board 203and are fixed to the bottom 202 a of the casing 202. The board 203 canthen slide along the pins 206. Furthermore, springs 210 are fitted onrespective pins 206 and, in particular, are arranged between the board203 and the bottom 202 a of the casing 202 so as to push the board 203against the heads 206 a of the pins 206, where it is blocked in aresting position substantially parallel to the plane of sliding PO. Theleft key 207 and the right key 208 are provided with respective pins212, which project towards the inside of the casing 202 and are shapedso as to touch on the board 203 when the respective keys 207, 208 arereleased (FIGS. 12 and 13). When, instead, one of the keys 207, 208 (theleft key 207, in the example of FIG. 14) is pressed, the correspondingpin 212 exerts a pressure on the board 203, which is tilted. Inparticular, the pins 212 act on the board 203 asymmetrically withrespect to the second axis Y, in such a way that the board 203 will betilted in opposite directions, again rotating about the second axis Y,according to whether the left key 207 or else the right key 208 has beenactuated. The springs 210 bring the board 203 back again into itsresting position against the heads 206 a of the pins 206 when the keys207, 208 are released.

The inertial sensor 204 is fixed to the board 203 and supplies a firstanalog detection signal S_(X), a second analog detection signal S_(Y),and a third analog detection signal S_(Z) to the microcontroller 205(see also FIG. 15). In this case, the first, second and third analogdetection signals S_(X), S_(Y), S_(Z) are correlated both to theaccelerations imparted on the inertial sensor 204 during thedisplacements of the mouse 200 and to the variations of inclination ofthe board 203. In fact, the inertial sensor 204 is sensitive also to theaction of the acceleration of gravity and responds by modifying thefirst analog detection signal S_(X), the second analog detection signalS_(Y), or the third analog detection signal S_(Z), when the direction ofthe corresponding detection axis X, Y, Z varies with respect to thedirection of the acceleration of gravity. In other words, a variation ininclination of one of the detection axes X, Y, Z is equivalent for theinertial sensor 204 to an acceleration along the same axis, and thus theinertial sensor 204 can be used as inclinometer.

The microcontroller 205 comprises: a reading unit 209, which convertsthe first, second, and third analog detection signals S_(X), S_(Y),S_(Z) into a first digital detection signal D_(X), a second digitaldetection signal D_(Y), and a third digital detection signal D_(Z),respectively; a processing unit 210; and an interface 211, forconnection to a computer system 12 of the type as the one illustrated inFIG. 6. In particular, the processing unit 210 is configured so as torecognize a click event when the first digital detection signal D_(X) isother than zero and, simultaneously, the third digital detection signalD_(Z) exceeds a pre-set threshold. Furthermore, the processing unit 210is configured so as to assign each recognized click event selectively tothe left key 207 or to the right key 208 on the basis of the sign of thefirst detection signal S_(X).

In particular, the processing unit 210 comprises: a first processingline 213 and a second processing line 214, which supply a firstdisplacement signal P_(X) and a second displacement signal P_(Y),respectively, of the mouse 200 on the basis of the first digitalacceleration signal D_(X) and of the second digital acceleration signalD_(Y) and a third processing line 215.

The third processing line 215 comprises: a recognition module 217, whichgenerates a recognition signal CKDET when the third digital detectionsignal D_(Z) exceeds a pre-set threshold; and a sign-discriminatormodule 218.

The sign-discriminator module 218 is selectively enabled by therecognition module 217 by means of the recognition signal CKDET and, onthe basis of the sign of the first digital detection signal D_(X),generates a first state signal LMB and a second state signal RMB, whichindicate the state (pressed/released) of the left key 207 and of theright key 208, respectively. In greater detail, the first state signalLMB presents a first value when the sign-discriminator module 218 isenabled and the first digital detection signal D_(X) has a first sign,determined by activation of the left key 207, and a second valueotherwise. The second state signal RMB presents the first value when thesign-discriminator module 218 is enabled and the first digital detectionsignal D_(X) has a second sign, determined by activation of the rightkey 208, and the second value otherwise. In practice, the first andsecond state signals LMB, RMB are normally at the second value (keyreleased) and switch to the first value when the left key 207 and theright key 208, respectively, are pressed.

The manual pointing device according to the invention is advantageousbecause a single inertial sensor and a single control device can be usedboth for detection of the movement in the plane of sliding, whichenables a pointer to be guided on the screen of a computer system, andfor detection of the click events. Instead, in traditional manualpointing devices separate sensors and control circuits are required fordetecting the movement and the click events. The pointing deviceaccording to the invention is also less subject to failures: inparticular, any problems linked to oxidation of the contacts fordetection of the click events are prevented.

Finally, it is evident that modifications and variations may be made tothe device and to the method described herein, without departing fromthe scope of the present invention.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to in this specification and/orlisted in the Application Data Sheet, are incorporated herein byreference, in their entirety.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A manual pointing device for a computer system, comprising: a first key structured to be manually actuatable by a user; and a click-event detection circuit coupled to the first key to detect actuation of the first key, the click-event detection circuit including an inertial-sensor circuit structured to detect mechanical stresses generated by actuation of the first key, the inertial-sensor circuit including a first detection axis and a second detection axis, perpendicular to one another and parallel to a surface of sliding of the manual pointing device at least in one operative configuration, and a third detection axis perpendicular to the first and second detection axes; the inertial-sensor circuit structured to supply a first detection signal, a second detection signal, and a third detection signal in response to mechanical stresses acting along the first detection axis, the second detection axis, and the third detection axis, respectively and further comprising a casing and wherein said inertial-sensor circuit is rigidly coupled to said casing for detecting mechanical stresses generated by actuation of said first key and that propagate along said casing.
 2. The device of claim 1, further comprising at least one second key that can be actuated manually by a user, in which said first and second keys are set in opposite positions with respect to said second detection axis.
 3. The device of claim 1 wherein said inertial-sensor circuit comprises accelerometers made with MEMS technology.
 4. The device of claim 1 wherein said click-event detection circuit includes a microcontroller and an interface for connection with a computer system.
 5. A manual pointing device for a computer system, comprising: at least one first key manually actuatable by a user; a click-event detection circuit coupled to the first key for detecting actuation of the first key, the click-event detection circuit comprising an inertial-sensor circuit to detect mechanical stresses generated by actuation of the first key, the inertial-sensor circuit comprising: a first detection axis and a second detection axis, perpendicular to one another and parallel to a surface of sliding of the manual pointing device at least in one operative configuration, and a third detection axis perpendicular to the first and second detection axes; the inertial-sensor circuit supplying a first detection signal, a second detection signal, and a third detection signal in response to mechanical stresses along the first detection axis, the second detection axis, and the third detection axis, respectively; the click-event detection circuit comprising a first processing circuit associated with the inertial-sensor circuit to supply a recognition signal having a first value in response to a mechanical stress that can be detected along the third detection axis, and further having a second value, otherwise, the recognition signal correlated to the third detection signal, the click-event detection circuit comprising a discrimination circuit to associate a detected click event selectively with one of the first and second keys on the basis of the first detection signal; and the discrimination circuit further comprising a second processing circuit associated with the inertial-sensor circuit to determine directions of propagation along the first detection axis of mechanical stresses generated by actuation of the first and second keys, on the basis of the first detection signal.
 6. The device of claim 5 wherein said discrimination means comprise a derivative module that supplies a derivative signal starting from said first detection signal.
 7. A manual pointing device for a computer system, comprising: at least one first key structured to be manually actuatable by a user; a click-event detection circuit coupled to the first key and structured to detect actuation of the first key, the click-event detection circuit including an inertial-sensor circuit structured to detect mechanical stresses generated by actuation of the first key, the inertial-sensor circuit including: a first detection axis and a second detection axis, perpendicular to one another and parallel to a surface of sliding of the manual pointing device at least in one operative configuration, and a third detection axis perpendicular to the first and second detection axes; the inertial-sensor circuit structured to supply a first detection signal, a second detection signal, and a third detection signal in response to mechanical stresses along the first detection axis, the second detection axis, and the third detection axis, respectively; the click-event detection circuit including a first processing circuit associated with the inertial-sensor circuit and structured to supply a recognition signal having a first value in response to a mechanical stress that can be detected along the third detection axis, and further having a second value, otherwise, the recognition signal correlated to the third detection signal, the click-event detection circuit including a discrimination circuit structured to associate a detected click event selectively with one of the first and second keys on the basis of the first detection signal; and the first processing circuit is connected to the discrimination circuit to enable and disable the discrimination circuit selectively on the basis of the recognition signal.
 8. The device of claim 7 wherein the discrimination circuit comprises an enabling element controlled by the first processing circuit.
 9. The device of claim 7, wherein the discrimination circuit further comprises a second processing circuit associated with the inertial-sensor circuit to determine directions of propagation along the first detection axis of mechanical stresses generated by actuation of the first and second keys, on the basis of the first detection signal, and further comprising a third processing circuit associated with the inertial-sensor circuit to determine a displacement of the manual pointing device on the basis of the first and second detection signals.
 10. A method for controlling a manual pointing device for a computer system, comprising the steps of: actuating manually at least one first key of the manual pointing device; and detecting a click event associated with actuation of the first key, the step of detecting a click event including detecting mechanical stresses generated by actuation of the first key using an inertial-sensor circuit that has a first detection axis and a second detection axis, perpendicular to one another and parallel to a surface of sliding of the manual pointing device at least in one operative configuration, and a third detection axis perpendicular to the first and second detection axes; the inertial-sensor circuit supplying a first detection signal, a second detection signal, and a third detection signal in response to mechanical stresses acting, respectively, according to the first detection axis, the second detection axis, and the third detection axis; and further comprising the step of rigidly coupling said inertia-sensor circuit to a casing of said pointing device and the step of detecting a click event comprises detecting mechanical stresses that are generated by actuation of said first key and which propagate through said casing of said pointing device.
 11. The method of claim 10, further comprising the step of recognizing a click event when mechanical stresses are detected in a direction perpendicular to a plane of sliding of said manual pointing device.
 12. The method of claim 11 wherein said first key and said second key of the pointing device are arranged opposite with respect to the second detection axis, and comprising the steps of detecting a direction of propagation of said mechanical stresses along said first detection axis and associating a detected click event selectively to one between said first key and said second key, on the basis of said direction of propagation. 